1. Field of the Invention
The invention is related to the field of communication systems, and in particular, to a communication system that has a higher digital bandwidth on an analog signal cycle by using a data structure.
2. Description of the Prior Art
Many residences and small businesses use Public Switched Telephone Networks (PSTNs) for telecommunications. The PSTNs offer analog services that transmit analog signals between a telephone company central office and a customer. The cabling that connects the customer to the central office can create a bottleneck. The cabling between the customer and the central office is known as the “last mile”. Communication providers continue to look for solutions to the bottleneck created by the “last mile”.
One solution is to offer digital services that transmit digital signals from the central office to the customer. Examples of digital services are ISDN and Digital Subscribe Line (DSL). Digital signals are transmitted at high frequencies. Unfortunately, the cabling between the central office and customers can be old and lower quality. The old, low-quality cabling can make a high frequency signal susceptible to distortion and can reduce the quality and reliability of the digital signal being transmitted to the customers. Also, the distance between the central office and the customer can affect high frequency signals.
When communication providers cannot offer digital services to customers, analog services might be the best option. The analog signal is generally less susceptible to distortion due to old, low-quality cabling. Those skilled in the art are aware that digital data can be transmitted over an analog signal. To do so in a communication system, the central office converts a digital signal to an analog signal using a conventional digital-to-analog (D/A) converter. The central office then transmits the analog signal to the customer over the “last mile”. The customer receives the analog signal and converts the analog signal to a digital signal using a conventional analog-to-digital (A/D) converter. Unfortunately, the current D/A converters are limited in the amount of digital data they can encode on an analog signal. Many D/A converters can only encode up to two digital data bits on a cycle of an analog signal. The bandwidth available to the customer is thus limited by the frequency of the analog signal. In such a situation, the bottleneck created by the “last mile” may not be avoided.